Anomalous Infrared Spectra of Hybridized Phonons in Type-I Clathrate Ba8Ga16Ge30

作者：Iwamoto Kei^*; Kushibiki Shunsuke; Honda Hironori; Kajitani Shuhei; Mori Tatsuya; Matsumoto Hideki; Toyota Naoki; Suekuni Koichiro; Avila Marcos A; Takabatake Toshiro

来源：Journal of the Physical Society of Japan, 2013, 82(2): 024601.

DOI：10.7566/JPSJ.82.024601

• rattling phonons
• hybridized phonon system
• phonon-impurity interactions
• THz time-domain spectroscopy
• clathrates

The optical conductivity spectra of the rattling phonons in the clathrate Ba8Ga16Ge30 are investigated in detail by use of the terahertz time-domain spectroscopy. The experiment has revealed that the lowest-lying vibrational mode of Ba(2)(2+) ions consist of a sharp Lorentzian peak at 1.2 THz superimposed on a broad tail weighted in the lower frequency regime around 1.0 THz. With decreasing temperature, an unexpected linewidth broadening of the phonon peak is observed, together with monotonic softening of the phonon peak and enhancement of the tail structure. These observed anomalies are discussed in terms of impurity scattering effects on the hybridized phonon system of rattling and acoustic phonons.

• 出版日期2013-2